[libvirt-users] machine='pc-q35-2.1' and sata controller

[John Snow]

On 03/22/2015 08:23 PM, Nerijus Baliunas wrote:
> On Thu, 12 Mar 2015 14:56:08 -0400 Laine Stump <laine at laine.org> wrote:
>
>> Here is the info straight from the author (I've also Cc'ed him to this
>> mail):
>>
>> ===============
>> The AHCI migration series is here:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05200.html
>
>> These are all just tests, at any rate -- the actual patch that enables
>> the migration is small and trivial and can be applied directly to
>> current upstream:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05202.html
>>
>> All of the requisites that make AHCI safe to migrate are already
>> upstream now.
>> ===========
>>
>> As I understand it, all except the last patch will be in qemu 2.3. Also,
>> he is actively soliciting people to test it, so if you've been wanting
>> to learn how to build qemu from source, now is your opportunity to
>> figure it out!
>
> Are the needed patches in 2.3.0-rc0?
> Is it possible to backport AHCI migration to RHEL 7.1 qemu or will it be too much work?
>
> Regards,
> Nerijus
>

The patches that improve the stability of AHCI migration are in 2.3-rc0. 
We still have not /enabled/ migration upstream, but editing to code to 
allow it is fairly trivial -- it's just a true/false value in the code.

My words of caution:

(1) We still have some bugs in the AHCI device which may necessitate 
changing the migration format of the device. Since we have not 
officially enabled migration, these format changes may leave you unable 
to migrate to later versions, because we are not currently being careful 
to maintain backwards compatibility with this "unreleased" device.

[If you are wondering what the probability of being unable to migrate to 
an official build where AHCI migration is supported is: Nearly 100%.]

(2) Because we have not enabled migration of AHCI officially, [And this 
is not enabled or supported in RHEL!] you may run into bugs. I wouldn't 
do this on a production system.

That said, if you do want to try it out on non-essential systems; for 
testing, development &c: I'd appreciate any bug reports.

See http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05202.html 
as mentioned above for the patch that simply enables migration.

--js